Luminescence enhancement of Ca3Sr3(VO4)4:Eu3+, Sm3+ red-emitting phosphor by charge compensation

Abstract

A series of red-emitting phosphors Ca3Sr3(VO4)4:0.05Eu3+; Ca3Sr3(VO4)4:0.05Eu3+, xSm3+; and Ca3Sr3(VO4)4:0.05Eu3+, 0.05Sm3+, yM+ (M = Li, Na, and K) were fabricated with the combustion method. The microstructure and photoluminescence properties of the phosphors were investigated via X-ray powder diffraction, scanning electron microscopy, and photoluminescence spectroscopy. The obtained results revealed that all samples perfectly matched the rhombohedral structure with R3c space group. The results showed that the luminescence properties of Eu3+ ions could evidently be improved by co-doping with Sm3+ ions. When the doping mole fraction of Sm3+ ions was 5%, the relative luminous intensity at 619 nm was maximal under an excitation of 464 nm. Moreover, incorporation of charge compensators (i.e., Li+, Na+, and K+) could improve both the luminescence intensity and thermal stability of phosphors under an excitation of 464 nm and this paper discusses and interprets the underlying reason. The optimal concentration of the charge compensator M+ (M = Li, Na, and K) was 5%. In particular, the Li+-doped sample exhibited significantly enhanced emission intensity and thermal stability under an excitation wavelength of 464 nm and its emission intensity was approximately 1.9-fold of that of Ca3Sr3(VO4)4:0.05Eu3+, 0.05Sm3+. Furthermore, the CIE chromaticity coordinate of Ca3Sr3(VO4)4:0.05Eu3+, 0.05Sm3+, 0.05Li+ phosphor was found to be closer to the standard red-emitting point (x = 0.67, y = 0.33) compared to Ca3Sr3(VO4)4:0.05Eu3+, 0.05Sm3+. The luminescence performance of Ca3Sr3(VO4)4:Eu3+, Sm3+, Li+ upon excitation with blue light radiation makes this a potential red-emitting phosphor for application in blue-based white light emitting diodes.